Is counselling 100% confidential, or will they tell someone if they think I'm a danger to other people?

It's all about the context, what are your reasons for doing this, what are you hoping to achieve? How often do you do it? Where abouts? What time of day?

They will look at the context if they feel as though you are a high risk to other members of the public, they will pass on info to either the police or other people involved in your care, or a doctor.

Similar applies with regards to harm to yourself

In the US, if you are a danger to others, if you've stated that you do or plan to do something that would harm another person or people, the counselors are legally obligated to do something about it.

It really depends on the situation. Obviously, if you tell them you are going to go out and harm someone, then they need to step in. But if you have irrational fears of harming someone, or that you feel like harming someone but would never actually act upon it, then it would and should be kept confidential. Hope this helps.

Edit: Could you go into a little bit more detail about why you drive with your eyes shut? Are you doing it intentionally in the the hope of causing an accident, or is it more of a compulsion due to anxiety-provoking thoughts?

Edit: Reckless and impulsive behaviour may be a sign of a disorder other than depression, i.e. bipolar disorder. Although I do not believe the information you share will go any further than your counsellor, you may want to ask your GP for a referral to a psychiatrist. Hope this helps.

I think that if you say you are suicidal or want to hurt someone they have to tell that.

someone should slash your tires.